1. Field of the Invention
This invention generally relates to daisy wheel printers. More specifically, this invention relates to a daisy wheel print element adapted to be housed and oriented in a cartridge during printing and storage. 2. Description of the Prior Art
Representing other work in this same area is U.S. Pat. application Ser. No. 767,250, filed Feb. 10, 1977, now U.S. Pat. 4,127,335 having Bogert et al. as inventors and entitled "Impact Printer With Cartridge Print Wheel". A daisy wheel printer print element is disclosed in this referenced application. There are a number of notable similarities between the print elements in the instant and referenced applications. In both applications there are generally disclosed (1) a print element which is to be housed in a cartridge and received by a printer carrier mechanism with minimum operator intervention, (2) a central hub and radially extending petals, (3) a centered bearing projection on the printing side of the print element central hub, (4) a drive opening radially displaced from the axis of rotation of the print element, and (5) an axially aligned annular extension located on the hammer impact side of the print element.
Several of the more important distinctions between the two applications and the advantages thereof as related to the instant application will now be addressed. To begin with, the central hub of the instant application is dish shaped with the protruding side thereof being on the impact side of the print element. The advantages of this are that (1) the print element, taken as a whole, can be made relatively thin and still resist warp, (2) with the print element being relatively thin, mass associated problems are reduced, (3) when the print element is utilized in a cartridge during both printing and storage, the petals are displaced from an adjacent cartridge surface, and (4) the surface area of the element in contact with the cartridge is at a minimum during storage. Another distinction is that the protruding side of the central hub of the instant application carries an orientation protrusion. The orientation protrusion is for mating with a matching orientation opening in the cartridge to latch the print element in a required rotational position for acceptance by a printer. The orientation protrusion has a stabilizing face surface for mating with a face of a drive hub for imparting dimensional stability to the print element a radial direction perpendicular to the axis of rotation of the element. Within the orientation protrusion which engulfs the axis of rotation of the print element is a depression, part of which is for reducing the mass of the print element and part of which is for mating with a portion of the selection motor drive hub. Extending from the bottom of the depression is a cylindrical extension having an axially aligned opening. The depth of the opening is sufficient to accept a selection motor drive shaft extending through the drive hub and impart additional dimensional stability to the print element. The advantages of the orientation protrusion associated structure are a low mass print element which can be properly oriented and located relative to the cartridge and drive hub, and be dimensionally stabilized by the drive hub.
Other distinctions and advantages of the instant application over the referenced application will be appreciated when reference is made to the accompanying drawing and the following description of the preferred embodiment.